In various duct installations, the end of one duct section often abuts and is supported from a side wall of a second duct section with the first duct section communicating with the second duct section through an opening formed in the side wall thereof against which the first duct section abuts. Various structures are utilized at the end of the first duct section for securement of the latter to the side wall of the second duct section, and the most frequently utilized structure comprises a separate heavy gauge mounting flange defining frame member which is welded about the end of the first duct section and abutted against and secured to the side wall of the second duct section about the opening formed therein. While this type of mounting is acceptable, the process of welding the mounting flange defining frame to the end of the first duct section involves considerable welding and often results in the mounting flange defining frame being warped (due to the welding heat) with the result that the juncture between the first duct end and the side wall of the second duct section is not airtight.
Accordingly, a need exists for an improved form of interconnection between a first duct section opening endwise laterally into and through the side wall of a second duct section.
Examples of duct connecting structures and other similar joint structures including some general structural and operational features of the instant invention are disclosed in U.S. Pat. Nos. 1,049,543, 1,824,499, 1,833,043, 2,255,658, 3,451,243, 3,782,764 and 4,060,265.